MySql-加入删除列中的重复项

Question

i am newbie in MySql. I don't know name of function (if its exist) so it's hard to find something. I have 2 tables.

software
id | name
---------
1  | xxxx
2  | yyyy

software_version
id | software_id | date
----------------------------------
1  | 2           | 2013-10-9 10:20
2  | 1           | 2013-10-9 10:21
3  | 1           | 2013-10-9 10:22
4  | 2           | 2013-10-9 10:23

Im looking for SQL command, that join this tables, order it by date and show only unique record. For these tables will looks like:

id | name | date
---------------------------
4  | yyyy | 2013-10-9 10:23
3  | xxxx | 2013-10-9 10:22

I found something about DISRINCT but it's unuseable for this i think (i found that it looks for duplicity of whole record). Maybe something with GROUP but I really don't know. How I said in MySql I can do only basic selects, inserts etc.

Even I dont know every type of JOIN so it could be some INNER JOIN or LEFT JOIN. There is so much types of JOIN but i dont see diference.

Thanks for every help!

Answer 1

You can use joins and for the most recent row for each software you can use selef join on the maxima of second table

select v.id,s.name,v.date from software s
join software_version v on (s.id=v.software_id)
join (select software_id ,max(date) date 
      from software_version group by software_id) v1
on(v.software_id =v1.software_id and v.date=v1.date)
order by v.date desc

Demo